Electronic devices assembled with thermally insulating layers

ABSTRACT

Provided herein are electronic devices assembled with thermally insulating layers.

BACKGROUND

1. Field

Provided herein are electronic devices assembled with thermallyinsulating layers.

2. Brief Description of Related Technology

As microelectronic circuitry continues to shrink in size and thecapacity of the circuitry in terms of functionality continues toincrease, the heat generated by the circuitry when in use becomes moreand more of a problem for manufacturers and end users. Put another way,the level of heat generated is related to the performance of thesemiconductor package, with more highly performing devices generatinggreater levels of heat. For instance, the semiconductor packagesassembled on the circuit board within the consumer electronic device,for instance, such as those found in central and graphics processingunits, chipsets, battery and voltage regulators, all generate heat as anormal by-product of operation. The semiconductor packages generate heatthat needs to be managed in order to increase the life of the package,minimize design limitations and increase performance of the package, andconsequently the life and performance of the consumer electronic device.

Thermal management materials are well known for dissipating heatgenerated by the circuitry and fans placed at strategic locations withinthe electronic device also draws heat away from the circuitry, orthermal module. The excess heat is diverted away from the semiconductorpackage to a heat sink or the thermal module with a thermal interfacematerial (“TIM”), oftentimes disposed between the semiconductor packageand the heat sink or thermal module.

However, these strategies to manage generated heat have created newproblems, as the hot air is directed away from the immediate environmentof the semiconductor package toward the interior of the housing of thedevice.

More specifically, in a conventional laptop or notebook computer (shownin FIG. 2), a housing exists under which are the components below thekeyboard (shown in FIG. 3). The components include a heat sink, a heatpipe (disposed above a CPU chip), a fan, a slot for the PCMIA card, ahard drive, a battery, and a bay for a DVD drive. The hard drive isdisposed under the left palm rest and the battery under the right.Oftentimes, the hard drive operates at high temperatures, resulting inuncomfortable palm rest touch temperatures, despite the use of coolingcomponents to dissipate this heat. This may lead to end user consumerdiscomfort due to hot temperatures attained at certain portions of theexterior of the device when the devices are used.

One solution to mute the high in use temperatures observed by the enduser at the palm rest position, for instance, is to use natural graphiteheat spreaders disposed at strategic locations. These heat spreaders arereported to distribute heat evenly while providing thermal insulationthrough the thickness of the material. One such graphite material isavailable commercially as eGraf® SpreaderShield™, from GrafTech Inc.,Cleveland, Ohio. [See M. Smalc et al., “Thermal Performance Of NaturalGraphite Heat Spreaders”, Proc. IPACK2005, Interpack 2005-73073 (July,2005); see also U.S. Pat. No. 6,482,520.]

Alternative solutions are desirable and would be advantageous, as thereis a growing need in the marketplace for ways in which to manage theheat generated by such semiconductor packages used in electronic devicesso that end user consumers do not feel discomfort due to the generatedheat when they are used. Balanced against this need is the recognitionthat designers of semiconductor chips will continue to reduce the sizeand geometry of the semiconductor chips and semiconductor packages butincrease their capacity, so as to make the electronic devices appealingfor the consumer, but in so doing causing the semiconductor chips andsemiconductor packages to continue to operate at elevated temperatureconditions. Accordingly, it would be advantageous to satisfy thisgrowing, unmet need, with alternative technologies to encourage thedesign and development of even more powerful consumer electronicdevices, which are not hot to the touch in operation.

This need has been unmet. Until now.

SUMMARY

Provided herein is a consumer electronic article of manufacturecomprising:

A housing comprising at least one substrate having an interior surfaceand an exterior surface;

A layer of thermally insulating elements disposed on at least a portionof the interior surface of the at least one substrate; and

At least one semiconductor package comprising an assembly comprising atleast one of

I.

a semiconductor chip;

a heat spreader; and

a thermal interface material therebetween (also known as a TIM1application)

II.

a heat spreader;

a heat sink; and

a thermal interface material therebetween (also known as a TIM2application).

Also, provided herein is a method of manufacturing such a consumerelectronic device.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts a cut away view of a circuit board on which is disposed aplurality of semiconductor packages and circuitry, together withelectronic materials ordinarily used in the assembly of the packagesthemselves and the assembly of the packages onto the board. Referencenumbers 1-18 refer to some electronic materials used in the packagingand assembly of semiconductors and printed circuit boards.

FIG. 2 depicts a laptop personal computer in the open position.

FIG. 3 depicts a top view of the contents of the laptop personalcomputer, beneath the keyboard and palm rests thereof.

FIG. 4 depicts a general schematic diagram of an electronic device.

DETAILED DESCRIPTION

As noted above, provided herein is a consumer electronic article ofmanufacture. This article of manufacture (or “device”) may be selectedfrom notebook personal computers, tablet personal computers or handhelddevices, for instance, music players, video players, still imageplayers, game players, other media players, music recorders, videorecorders, cameras, other media recorders, radios, medical equipment,domestic appliances, transportation vehicle instruments, musicalinstruments, calculators, cellular telephones, other wirelesscommunication devices, personal digital assistants, remote controls,pagers, monitors, televisions, stereo equipment, set up boxes, set-topboxes, boom boxes, modems, routers, keyboards, mice, speakers, printers,and combinations thereof.

The device includes:

A housing comprising at least one substrate having an interior surfaceand an exterior surface;

A layer of thermally insulating elements disposed on at least a portionof the interior surface of the at least one substrate; and

At least one semiconductor package comprising an assembly comprising atleast one of

I.

a semiconductor chip;

a heat spreader; and

a thermal interface material therebetween, or

II.

a heat spreader;

a heat sink; and

a thermal interface material therebetween.

The device may also include a venting element to disperse heat generatedfrom the semiconductor assembly away from the device.

Of course, the consumer electronic device is provided with a powersource to energize the semiconductor package(s).

The semiconductor package may be formed with a die attach materialdisposed between a semiconductor chip and a circuit board to securelyadhere the chip to the board. Wire bonding forms the electricalinterconnection between the chip and the board. This die attach materialis oftentimes a highly filled material with a thermosetting resinmatrix. The matrix may be composed of epoxy, maleimide, itaconimide,nadimide and/or (meth)acrylate. The filler may be conductive ornon-conductive. In some instances, the die attach material is thermallyconductive, in which case it too aids in dissipating heat away from thesemiconductor package. Representative commercially available examples ofsuch die attach materials include QMI519HT from Henkel Corporation.

Alternatively, the semiconductor package may be formed with asemiconductor chip electrically connected to a circuit board with solderinterconnects in a space therebetween. In that space an underfillsealant may be disposed. The underfill sealant will also have athermosetting matrix resin, which like the die attach material may becomposed of epoxy, maleimide, itaconimide, nadimide and/or(meth)acrylate. The underfill sealant is ordinarily also filled.However, the filler is generally non-conductive and used for the purposeof accommodating differences in the coefficients of thermal expansion ofthe semiconductor die and the circuit board. Representative commerciallyavailable examples of such underfill sealants include HYSOL FP4549HTfrom Henkel Corporation.

Once the semiconductor package has been positioned onto the circuitboard and attached thereto oftentimes by a surface mount adhesive, achip bonder, or chip scale package underfill sealant, the package may beovermolded with mold compound in order to protect the package from amongother things environmental contaminants. The mold compound is oftentimesepoxy or benzoxazine based. GR750 is an example of an epoxy moldcompound, available commercially from Henkel Corporation, designed toimprove thermal management in semiconductor devices.

Solder pastes are used at various portions on the circuit board toattach semiconductor packages and assemblies, in an electricallyinterconnected manner. One such solder paste is available commerciallyfrom Henkel Corporation under the tradename MULTICORE Bi58LM100. Thislead free solder paste is designed for applications where thermalmanagement is desirable.

To effectively manage the heat generated by semiconductor chips andsemiconductor packages, a thermal interface material may be used withany heat-generating component for which heat dissipation is required,and in particular, for heat-generating components in semiconductordevices. In such devices, the thermal interface material forms a layerbetween the heat-generating component and the heat sink and transfersthe heat to be dissipated to the heat sink. The thermal interfacematerial may also be used in a device containing a heat spreader. Insuch a device, a layer of thermal interface material is placed betweenthe heat-generating component and the heat spreader, and a second layerof thermal interface material is placed between the heat spreader andthe heat sink.

The thermal interface material may be a phase change material, such asone commercially available from Henkel Corporation under the tradenamesPOWERSTRATE EXTREME, PowerstrateXtreme or PSX. Packaged as afree-standing film between two release liners and supplied as a die cutperform to match a wide variety of applications, this thermal interfacematerial is a reworkable phase change material suitable for use forinstance between a heat sink and variety heat dissipating components.The material flows at the phase change temperature, conforming to thesurface features of the components. The thermal interface material whenin the form of a phase change material has a melting point ofapproximately 51° C. or 60° C.

Upon flow, air is expelled from the interface, reducing thermalimpedance, performing as a highly efficient thermal transfer material.

The thermal interface material may be constructed from (a) 60% to 90% byweight of paraffin; (b) 0% to 5% by weight of resin; and (c) 10% to 40%by weight of metal particle, such as an electrically-conductive filler.The electrically-conductive filler is ordinarily one selected fromgraphite, diamond, silver, and copper. Alternatively, theelectrically-conductive filler may be aluminum, such as a sphericalalumina.

The metal particles suitable for use in the thermal interface materialmay be fusible metal particles, typically low melting point metals ormetal alloys used as solders. Examples of such metals include bismuth,tin, and indium, and may also include silver, zinc, copper, antimony,and silver coated boron nitride. In one embodiment the metal particlesare selected from tin, bismuth, or both. In another embodiment, indiumwill also be present. Alloys of the above metals also can be used.

An eutectic alloy of tin and bismuth powder (melting point 138° C.), ina weight ratio of tin to bismuth of Sn48Bi52 may also be used,particularly in combination with indium powder (melting point 158° C.),in which the indium is present in a weight ratio of 1:1 with the Sn:Bialloy.

The metal particles and/or alloys should be present in the compositionin a range from 50 to 95 weight percent of the thermal interfacematerial.

The thermal interface material may also be a thermal grease, such as onecommercially available from Henkel Corporation under the tradedesignations TG100, COT20232-3611 or COT20232-36E1. TG100 is a thermalgrease designed for high-temperature heat transfer. In use, TG100 isplaced between heat generating devices and the surfaces to which theyare mounted or other heat dissipating surfaces. This product deliversexcellent thermal resistance, offers high thermal conductivity andvirtually no evaporation over a wide operating temperature range. Inaddition, COT20232-36E1 and COT20232-3611 are TIM1 type materials,designed in this instance for high power flip chip applications. Theseproducts contain a soft gel polymer or curable matrix, which after cureforms an interpenetrating network with a low melting point alloytherewithin. The low melting point alloy may be fusible metal solderparticles, particularly those substantially devoid of added lead,comprising an elemental solder powder and optionally a solder alloy.

The thermal interface material in use should have a thermal impedance ofless than 0.2 (° C. cm²/Watt).

The housing comprises at least two substrates and oftentimes a pluralityof substrates. The substrates are dimensioned and disposed to engage oneanother.

The layer of thermally insulating elements is disposed on at least aportion of the interior surface of the at least one substrate thatcomprises the housing, the complementary exterior surface of which comesinto contact with the end user when in use. So, with reference to FIG.3, palm rests would be good examples of this location on a lap top ornotebook personal computer. The thermally insulating elements maycomprise a gas, such as air. The gas may be housed within a hollowsphere-like vessel.

The thermally insulating elements may comprise a gas disposed withininterstices of a substantially solid sphere-like particle.Representative commercially available examples of such thermallyinsulating elements include those sold under the AEROGEL NANOGELtradename by Degussa Corporation. They are described by the manufactureras lightweight, insulating silica materials, composed of a latticenetwork of glass strands with very small pores, composed from up to 5%solids and 95% air. This structure, it is reported, creates superiorinsulating, light transmitting and water repelling properties. Thesilica materials are a nanoporous silica with an average pore size of 20nanometers. The small pore size and structure traps the flow of air toprevent heat loss and solar heat gain.

Prior to application the desired surface, the thermally insulatingelements are contacted with a carrier vehicle, so as to form asuspension, dispersion or emulsion, at a concentration of 25% to 99% byvolume in a liquid carrier vehicle. The carrier vehicle may be anyliquid, though desirable ones carry no, or at most a low level of,environmental regulation and labeling requirements and should not causeor tend to cause agglomeration of the thermally insulating elements. Theliquid carrier vehicle may be polar or non-polar. Water is a desirablecarrier vehicle, as is lower alcohols. A polymeric emulsion may also bea desirable carrier vehicle.

The thermally insulating elements are applied to the surface indispersion, suspension or emulsion form in a liquid carrier vehicle,such as by spraying. After application, the liquid carrier vehicle isremoved under exposure to temperature conditions modestly higher thanroom temperature. The thermally insulating elements should form acoating on the surface of the substrate. The so-formed coating is thickenough to aid in creating a barrier to heat transmission through thesubstrate from the heat generated from the semiconductor packages whenin use, but not so thick so as to interfere with the assembly and/oroperation of the consumer electronic device.

With reference to FIG. 1, a cut way view of a circuit board is shown. Onthe circuit board is disposed a plurality of semiconductor packages andcircuitry, together with electronic materials ordinarily used in theassembly of the packages themselves and the assembly of the packagesonto the board, and a portion of the housing of the electronic device inwhich the circuit board is to be used. In FIG. 1, 1 refers to surfacemount adhesives (such as LOCTITE 3609 and 3619); 2 refers to thermalinterface materials, as described in more detail herein; 3 refers to lowpressure molding materials (such as MM6208); 4 refers to flip chip onboard underfill such as HYSOL FP4531); 5 refers to liquid encapsulantsglob top (such as HYSOL E01016 and E01072); 6 refers to siliconeencapsulants (such as LOCTITE 5210); 7 refers to gasketing compounds(such as LOCTITE 5089); 8 refers to a chip scale package/ball grid arrayunderfill (such as HYSOL UF3808 and E1216); 9 refers to a flip chip airpackage underfill (such as HYSOL FP4549 HT); 10 refers to coating powder(such as HYSOL DK7-0953M); 11 refers to mechanic molding compound (suchas HYSOL LL-1000-3NP and GR2310); 12 refers to potting compound (such asE&C 2850FT); 13 refers to optoelectronic (such as Ablestik AA50T); 14refers to die attach (such as Ablestick 0084-1LM1SR4, 8290 and HYSOLOM1529HT); 15 refers to conformal coating (such as LOCTITE 5293 andPC40-UMF); 16 refers to photonic component and assembly materials (suchas STYLAST 2017M4 and HYSOL OTO149-3); 17 refers to semiconductor moldcompound; and 18 refers to solder (such as Multicore BI58LM100AAS90V and97SCLF318AGS88.5). Each of these products is available for salecommercially from Henkel Corporation, Irvine, Calif.

The circuit board A of FIG. 1 is disposed within the interior of thehousing of an electronic device (not shown). On at least a portion of aninwardly facing surface of a substrate which comprises the housing ofthe electronic device is coated a layer of thermally insulating elements(not shown).

As shown in FIG. 4, electronic device 100 may include housing 101,processor 102, memory 104, power supply 106, communications circuitry108-1, bus 109, input component 110, output component 112, and coolingcomponent 118. Bus 109 may include one or more wired or wireless linksthat provide paths for transmitting data and/or power, to, from, orbetween various components of electronic device 100 including, forexample, processor 102, memory 104, power supply 106, communicationscircuitry 108-1, input component 110, output component 112, and coolingcomponent 118.

Memory 104 may include one or more storage mediums, including, but notlimited to, a hard-drive, flash memory, permanent memory such asread-only memory (“ROM”), semi-permanent memory such as random accessmemory (“RAM”), any other suitable type of storage component, and anycombinations thereof. Memory 104 may include cache memory, which may beone or more different types of memory used for temporarily storing datafor electronic device applications.

Power supply 106 may provide power to the electronic components ofelectronic device 100, either by one or more batteries or from a naturalsource, such as solar power using solar cells).

One or more input components 110 may be provided to permit a user tointeract or interface with device 100, such as by way of an electronicdevice pad, dial, click wheel, scroll wheel, touch screen, one or morebuttons (e.g., a keyboard), mouse, joy stick, track ball, microphone,camera, video recorder, and any combinations thereof.

One or more output components 112 can be provided to present information(e.g., textual, graphical, audible, and/or tactile information) to auser of device 100, such as by way of audio speakers, headphones, signalline-outs, visual displays, antennas, infrared ports, rumblers,vibrators, and any combinations thereof.

One or more cooling components 118 can be provided to help dissipateheat generated by the various electronic components of electronic device100. These cooling components 118 may take various forms, such as fans,heat sinks, heat spreaders, heat pipes, vents or openings in housing 101of electronic device 100, and any combinations thereof.

Processor 102 of device 100 may control the operation of many functionsand other circuitry provided by device 100. For example, processor 102can receive input signals from input component 110 and/or drive outputsignals through output component 112.

Housing 101 should provide at least a partial enclosure to one or moreof the various electronic components that operate electronic device 100.Housing 100 protects the electronic components from debris and otherdegrading forces external to device 100. Housing 101 may include one ormore walls 120 that define a cavity 103 within which various electroniccomponents of device 100 can be disposed. Housing openings 151 may alsoallow certain fluids (e.g., air) to be drawn into and discharged fromcavity 103 of electronic device 100 for helping to manage the internaltemperature of device 100. Housing 101 can be constructed from a varietyof materials, such as metals (e.g., steel, copper, titanium, aluminum,and various metal alloys), ceramics, plastics, and any combinationsthereof.

Rather than being provided as a single enclosure, housing 101 may alsobe provided as two or more housing components. Processor 102, memory104, power supply 106, communications circuitry 108-1, input component110, and cooling component 118 may be at least partially containedwithin a first housing component 101 a, for instance, while outputcomponent 112 may be at least partially contained within a secondhousing component 101 b.

EXAMPLE

The following components were placed in a vessel with stirring; anacrylic emulsion (HYCAR 26138), 30%; Surfactant (PLURONIC P84), 3%;Defoamer (BYK019), 1%; AEROGEL, 9%, and Water, 57%.

The mixture was stirred for a period of time of 60 minutes to dispersethe AEROGEL silica particles. The mixture was then sprayed on asubstrate and dried at a temperature of 100° C. for a period of time of30 minutes to produce a tacky pressure sensitive adhesive (“PSA-A”)film.

A 0.1 mm coating of the PSA-A was placed on a test die, and exposed to atemperature of 50° C. to produce a 6.8° C. temperature drop. A filmprepared in a similar manner though without the AEROGEL silica particlesand likewise placed on a test die produced a 2° C. temperature drop.

What is claimed is:
 1. A consumer electronic article of manufacturecomprising: A housing comprising at least one substrate having aninterior surface and an exterior surface; A layer of thermallyinsulating elements disposed on at least a portion of the interiorsurface of the at least one substrate; and At least one semiconductorpackage comprising an assembly comprising at least one of I. asemiconductor chip; a heat spreader; and a thermal interface materialtherebetween, or II. a heat spreader; a heat sink; and a thermalinterface material therebetween.
 2. The article of claim 1, furthercomprising a venting element to disperse generated heat from thesemiconductor assembly from the article.
 3. The article of manufactureof claim 1, wherein the housing comprises at least two substrates. 4.The article of manufacture of claim 1, wherein the housing comprises aplurality of substrates.
 5. The article of manufacture of claim 1,wherein the substrates are dimensioned and disposed to engage oneanother.
 6. The article of manufacture of claim 1, wherein the layer ofthermally insulating elements is disposed on at least a portion of theinterior surface of the at least one substrate, the complementaryexterior surface of which comes into contact with the end user when inuse.
 7. The article of manufacture of claim 1, wherein the thermallyinsulating elements comprise a gas.
 8. The article of manufacture ofclaim 1, wherein the thermally insulating elements comprise air.
 9. Thearticle of manufacture of claim 1, wherein the thermally insulatingelements comprise a gas disposed within interstices of a substantiallysolid sphere-like particle.
 10. The article of manufacture of claim 1,wherein the thermally insulating elements are used at a concentrationwithin the range of 25% to 99% by volume in a liquid carrier vehicle.11. The article of manufacture of claim 1, wherein the thermallyinsulating elements are applied to the surface in dispersion or asuspension in a liquid carrier vehicle.
 12. The article of manufactureof claim 1, wherein the thermally insulating elements are applied to thesurface in a dispersion or a suspension in a liquid carrier vehiclecomprising water.
 13. The article of manufacture of claim 1, wherein thethermally insulating elements are applied to the surface in a dispersionor a suspension in a liquid carrier vehicle comprising polymericemulsions.
 14. The article of manufacture of claim 1, wherein thethermal interface material comprises a phase change material.
 15. Thearticle of manufacture of claim 1, wherein the thermal interfacematerial comprises thermal grease.
 16. The article of manufacture ofclaim 1, wherein the thermal interface material comprises athermally-conductive composition for facilitating the transfer of heatfrom an electronic component to a heat sink comprising: (a) 60% to 90%by weight of paraffin; (b) 0% to 5% by weight of resin; and (c) 10% to40% by weight of an electrically-conductive filler.
 17. The article ofmanufacture of claim 1, wherein the electrically-conductive filler isselected from the group consisting of graphite, diamond, silver, copperand alumina.
 18. The article of manufacture of claim 1, wherein thecomposition has a melting point of approximately 51° C.
 19. The articleof manufacture of claim 1, wherein the composition has a melting pointof approximately 60° C.
 20. The article of manufacture of claim 1,wherein the thermal interface material comprises a curable matrixmaterial; fusible metal solder particles substantially devoid of addedlead, comprising an elemental solder powder and optionally a solderalloy; and optionally, a catalyst.
 21. The article of manufacture ofclaim 1, wherein the thermal interface material has a thermal impedanceof less than 0.2 (° C. cm²/Watt).
 22. The article of manufacture ofclaim 1, wherein the article is a notebook personal computer, tabletpersonal computer or a handheld device.